The present invention relates to a method for lining pipes of an underground pipeline such as town gas pipeline or water pipeline, and more particularly to a method for lining pipes with plastics in order to repair old pipes.
A conventional lining method for old pipes is that fine droplets of thermosetting plastics such as epoxy resin are carried through the pipes by air stream produced by a compressor or blower, so that the inner walls of the pipes may be coated with the plastics. In the conventional method, the velocity and pressure of carrier air are comparatively high, for example the velocity is 80 m/sec.-100 m/sec. and the pressure is 2 Kg/cm.sup.2 -7 Kg/cm.sup.2. On the other hand, the majority of old pipes are pierced with a plurality of holes caused by corrosion. Accordingly, plastics supplied at a high. pressure flows out through the holes, so that the holes are not blocked with the plastics. In addition, it may happen that the holes are expanded or the pipes are broken by the plastics.
In order to eliminate such disadvantages in the conventional method, the inventor has proposed a method for lining pipes in a pipeline comprising connecting an end opening of the pipeline to a vacuum generator, and sucking the air in the pipeline by the vacuum generator together with plastics mist, whereby pipes of the pipeline may be uniformly lined with plastics with the blocking of holes.
However, in such a method, the plastics must be held at a low viscosity, so that the plastics may be carried by carrier air at a low pressure. It will be noted that it is difficult to form a thick lining layer with plastics having a low viscosity. Therefore, it is impossible to reinforce the pipe with the liner to have a necessary strength as a gas pipe.